Method for producing contact lenses

ABSTRACT

The invention provides a method producing contact lenses, comprising the step of: separating the mold into the male and female mold halves, with the silicone hydrogel contact lens adhered on one of the male and female mold halves; cooling the lens-adhere mold half with the molded silicone hydrogel contact lens adhered thereon; bringing a shaped ultrasonic horn in direct contact with at least one area of a non-optical surface of the female mold half or the male mold half having the molded silicone hydrogel contact lens attached thereon; and applying a ultrasonic vibrational energy to the at least one area of the non-optical surface of the female mold half or the male mold half having the molded silicone hydrogel contact lens attached thereon so as to separate the molded silicone hydrogel contact lens from the mold half attached thereon.

The present invention relates to an improved method for producingcontact lenses, in particular silicone hydrogel contact lenses.

BACKGROUND OF THE INVENTION

Silicone hydrogel contact lenses can be manufactured economically inlarge numbers by a conventional full-mold process involving disposablemolds, the examples of which are disclosed in, for example, PCT patentapplication no. WO/87/04390, in EP-A 0 367 513 or in U.S. Pat. No.5,894,002. In a conventional molding process, a predetermined amount ofa polymerizable or crosslinkable material typically is introduced into adisposable mold comprising a female (concave) mold half and a male(convex) mold half. The female and male mold halves cooperate with eachother to form a mold cavity having a desired geometry for a contactlens. Normally, a surplus of polymerizable or crosslinkable material isused so that when the male and female halves of the mold are closed, theexcess amount of the material is expelled out into an overflow areaadjacent to the mold cavity. The polymerizable or crosslinkable materialremaining within the mold is polymerized or cross-linked by means ofactinic radiation (e.g., UV irradiation, ionized radiation, microwaveirradiation or by means of heating. Both the starting material in themold cavity and the excess material in the overflow area are therebyhardened. Subsequently, the mold is opened and the polymerized but asyet unhydrated contact lens is removed and further processed.

Unfortunately, it is not possible as a rule to predict reliably to whichof the two mold halves the contact lens will adhere: in some cases itadheres to the male mold half (mold half with the convex optical moldingsurface) and, in others, it stays in the female mold half (mold halfwith the concave optical molding surface). After opening of the mold,therefore, a check must be made in every case to discover on or in whichmold half the polymerized but as yet unhydrated contact lens is located.

After mold separation, the lens on its respective mold half (male orfemale) together is subjected to extraction with an organic solvent(e.g., IPA (isopropyl alcohol)). This is done because the lens isdifficult to be removed from the mold half due to a strong adhesionbetween the lens and the mold half. It is believed that this strongadhesion is due to the tackiness of the surface of a silicone hydrogellens so produced. If the lens is removed from the mold half by force,the lens can adhere to itself (curl) and lens handling can be difficultand/or the lens can be damaged due to extreme surface tackiness.

After the extraction, the lens, still on the mold half, is equilibratedin water and then removed from the mold half. However, the lens stilladheres onto the mold surface, thus, a solvent mixture is used todeblock (or dislodge, or delensing) the lens. The removed lens isfurther subjected to other process, such as, for example, plasmatreatment, hydration, sterilization, etc.

In general, extraction and equilibration of lenses are carried out inbatch processes. There are some disadvantages associated with each lensassociated with one mold half. First, mold halves takes up valuablespace in an extraction or equilibration tank and therefore reduce thecapacity of extraction which can be carried out in each tank. Second,lens flashes can be partially or completely dissolve in an extractionbath. Any dissolution of lens flashes can potentially reduce extractionefficiency. Third, lens flashes may be still attached to the lens evenafter extraction and equilibration. Any lens with flashes attachedthereto will be rejected and as such, production yield can be decreased.It would be desirable to have a step of removing, also known as“deblocking” or “dislodging” or “delensing”, the lens from thelens-adhering mold half, such as, e.g., isopropyl alcohol (IPA), can beused to dislodge a silicone-hydorgel lens from its adhering mold half.The solvent swells the lens and helps reduce the forces holding the lensto the mold half surface. However, once a lens is swollen, the largesize of the lens makes it difficult to handle due to lack of mechanicalstrength. In addition, the lens after swelling in an organic solvent(e.g., IPA) may still be sticky or tacky.

PCT published international patent application No. WO 01/30558 describesa different approach for dislodging a lens from its adhering mold half,by lowering the temperature of the contact lens with a cryogenicmaterial to a temperature and for a time sufficient for the lens torelease from its adhering mold half without the application of externalforces. The lowering of the temperature of the contact lens isaccomplished by direct or indirect contact with a cryogenic substance,such as liquid nitrogen, liquid helium, liquid carbon dioxide, or solidcarbon dioxide (“dry ice”). In physics, cryogenics is the production andbehaviour of materials at very low temperatures. According to Wikipedia,scientists define a gas to be cryogenic if it can be liquefied at orbelow −150° C. (123 K; −238° F.). The U.S. National Institute ofStandards and Technology considers the field of cryogenics as thatinvolving temperatures below −180° C. (93 K; −292° F.). This is alogical dividing line, since the normal boiling points of the so-calledpermanent gases (such as helium, hydrogen, neon, nitrogen, oxygen, andnormal air) lie below −180° C. while the Freon refrigerants,hydrocarbons, and other common refrigerants have boiling points above−180° C. When a cryogenic substance is used to cool down a siliconehydrogel lens, the surface tackiness temporarily freezes. The mold halfbecause of reduction in the tackiness and probably lens size reductionso much that the lens separate from the mold. However, the lens afterseparation becomes tacky again in air, which makes the lens handlingdifficult. In addition, use of a cryogenic substance can increasesproduct cost significantly.

Therefore, there is a need not only to provide a process forcasting—molding contact lenses with enhanced quality and enhanced yieldachieved by omitting the previously required check to discover on or inwhich mold half the contact lens is located after the mold has beenopened, but also to provide a process which permit silicone hydrogellens to be separated from lens adhering mold half, and do not requireliquid soaks.

SUMMARY OF THE INVENTION

The invention is directed to a method for producing contact lenses,comprising:

a) providing a mold including a male mold half having a first moldingsurface and a female mold half having a second molding surface, whereinthe male and female mold halves are configured to receive each othersuch that a mold cavity is formed between the first and second moldingsurfaces when the mold is closed;b) dispensing an amount of a silicone hydrogel lens-forming materialinto the female mold halves;c) mating the male and female mold halves to close the mold;d) curing thermally or actinically the silicone hydrogel lens-formingmaterial located in the mold cavity, thereby forming a silicone hydrogelcontact lens within the lens mold;e) separating the mold into the male and female mold halves, with themolded silicone hydrogel contact lens adhered on a lens-adhered moldhalf which is one of the male and female mold halves;f) cooling the lens-adhere mold half with the molded silicone hydrogelcontact lens adhered thereon to a temperature between minus five degreeCelsius and fifteen degree Celsius and provided that a liquid nitrogen,liquid helium or solid carbon dioxide is not used to cool thelens-adhere mold half;g) bringing a shaped ultrasonic horn in direct contact with at least onearea of a non-optical surface of the cooled lens-adhered mold half withthe molded silicone hydrogel contact lens attached thereon;h) applying a ultrasonic vibrational energy to the at least one area ofthe non-optical surface of the lens-adhered mold half having the moldedsilicone hydrogel contact lens attached thereon so as to release themolded silicone hydrogel contact lens from the lens-adhered mold half.

The invention is also directed to an apparatus for delensing a hydrogelcontact lens from the lens adhering mold half, separating a moldedhydrogel contact lens from a female mold half or a male mold halfattached thereon, the apparatus comprising:

means for holding the female mold half or the male mold half havinghydrogel contact lens attached thereon stationary, means for cooling thelens-adhere mold half with the silicone hydrogel contact lens adheredthereon;an ultrasonic energy horn is shaped to direct contact with at least onearea of a non-optical surface of the female mold half or the male moldhalf having the molded hydrogel contact lens attached thereon,a power supply, a converter and a booster coupled to the horn to form aultrasonic welding system for generating ultrasonic energy of afrequency and amplitude, and for a duration necessary to separate themolded hydrogel contact lens from the female mold half or the male moldhalf attached thereon.

The present invention provides the foregoing and other features, and theadvantages of the invention will become further apparent from thefollowing detailed description of the presently preferred embodiments,read in conjunction with the accompanying figures. The detaileddescription and figures are merely illustrative of the invention and donot limit the scope of the invention, which is defined by the appendedclaims and equivalents thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a mold according to a preferredembodiment of the invention.

FIG. 2 illustrates schematically a process for separating the male andfemale mold halves of a lens-forming mold according to the invention andan apparatus for performing a method of the invention.

FIG. 3 illustrates an ultrasonic welding system.

FIG. 4 illustrates a flat ultrasonic horn seated on extended flat edgesurround the outer concave surface of the male mold half.

FIGS. 5A and 5B illustrate a convex ultrasonic horn is seated within theouter concave portion of male half mold half.

FIG. 6 illustrates a flat ultrasonic horn is sized to be approximatelythe outer diameter of the female mold half.

FIGS. 7A and 7B illustrate a concave ultrasonic horn seated within theouter convex portion of female half mold half.

FIG. 8 illustrates a cold blower to cool the outer convex portion offemale half mold half.

FIG. 9 illustrates a cold tube with a closed surface and with cold airinlet and outlet to cool the outer concave portion (non-optical side) ofmale half mold half.

FIG. 10 illustrates a cold tube without a closed surface but with coldair inlet and outlet to cool the outer concave portion (non-optical) ofmale half mold half.

DESCRIPTION OF PREFERRED EMBODIMENTS

Reference now will be made in detail to the embodiments of theinvention, one or more examples of which are set forth below. Eachexample is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that various modifications and variations can be madein the present invention without departing from the scope or spirit ofthe invention. For instance, features illustrated or described as partof one embodiment, can be used on another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present inventioncover such modifications and variations as come within the scope of theappended claims and their equivalents. Other objects, features andaspects of the present invention are disclosed in or are obvious fromthe following detailed description. It is to be understood by one ofordinary skill in the art that the present discussion is a descriptionof exemplary embodiments only, and is not intended as limiting thebroader aspects of the present invention.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Generally, the nomenclatureused herein and the laboratory procedures are well known and commonlyemployed in the art. Conventional methods are used for these procedures,such as those provided in the art and various general references. Wherea term is provided in the singular, the inventors also contemplate theplural of that term.

A “hydrogel” refers to a polymeric material which can absorb at least 10percent by weight of water when it is fully hydrated. Generally, ahydrogel material is obtained by polymerization or copolymerization ofat least one hydrophilic monomer in the presence of or in the absence ofadditional monomers and/or macromers.

A “silicone hydrogel” refers to a hydrogel obtained by copolymerizationof a polymerizable composition comprising at least onesilicone-containing vinylic monomer or at least one silicone-containingmacromer.

A “vinylic monomer”, as used herein, refers to a low molecular weightcompound that has an ethylenically unsaturated group and can bepolymerized actinically or thermally. Low molecular weight typicallymeans average molecular weights less than 700 Daltons.

The term “olefinically unsaturated group” or “ethylefinicallyunsaturated group” is employed herein in a broad sense and is intendedto encompass any groups containing at least one >C═C< group. Exemplaryethylenically unsaturated groups include without limitation acryloyl,methacryloyl, allyl, vinyl, styrenyl, or other C═C containing groups.

As used herein, “actinically” in reference to curing or polymerizing ofa polymerizable composition or material means that the curing (e.g.,crosslinked and/or polymerized) is performed by actinic irradiation,such as, for example, UV irradiation, ionized radiation (e.g. gamma rayor X-ray irradiation), microwave irradiation, and the like. Thermalcuring or actinic curing methods are well-known to a person skilled inthe art.

A “hydrophilic vinylic monomer”, as used herein, refers to a vinylicmonomer which as a homopolymer typically yields a polymer that iswater-soluble or can absorb at least 10 percent by weight water.

A “hydrophobic vinylic monomer”, as used herein, refers to a vinylicmonomer which as a homopolymer typically yields a polymer that isinsoluble in water and can absorb less than 10 percent by weight water.

A “macromer” refers to a medium and high molecular weight compound orpolymer that contains ethylenically unsaturated groups and can bepolymerized actinically or thermally. Medium and high molecular weighttypically means average molecular weights greater than 700 Daltons.

A “polymer” means a material formed by polymerizing/crosslinking one ormore monomers, macromers and or oligomers.

“Molecular weight” of a polymeric material (including monomeric ormacromeric materials), as used herein, refers to the number-averagemolecular weight unless otherwise specifically noted or unless testingconditions indicate otherwise.

As used herein, a “prepolymer” refers to a starting polymer which can becured (e.g., crosslinked and/or polymerized) actinically or thermally toobtain a crosslinked and/or polymerized polymer having a molecularweight much higher than the starting polymer.

A “chain-extended polysiloxane vinylic crosslinker” refers to a compoundcomprising at least two ethylenically-unsaturated groups and at leasttwo polysiloxane segments each pair of which is linked by one divalentradical.

A “lens-forming material” refers to a polymerizable composition whichcan be cured (i.e., polymerized and/or crosslinked) thermally oractinically to obtain a crosslinked polymer. Lens-forming materials arewell known to a person skilled in the art.

A “non-optical surface of a mold half” refers to mold half surface whichdoes not contact the lens forming material during cast molding a contactlens.

The invention generally relates to a method for separating mold anddislodging (or removing or de-blocking) of a silicone hydrogel contactlens from a mold after lens curing and before lens extraction. Theinvention is partly based on the discovery that although use ofultrasonic vibration energy can be used to dislodge a silicone-hydrogellens from its adhering mold half as illustrated in patent applicationSer. No. 15/841,647, ultrasonic vibration energy alone may not enoughfor dislodge a silicone-hydrogel lens which has a sticky surface. Theinvention is also partly based on the discovery that the problem ofdislodging a sticky silicone-hydrogel lens from its adhering mold halfis solved first by cooling the lens-adhere mold half with the siliconehydrogel contact lens adhered thereon and then further use of ultrasonicvibration energy to dislodge a silicone-hydrogel lens from its adheringmold half.

Although the inventors do not wish to be bound by any particular theory,it is believed that cooling the lens-adhere mold half with the siliconehydrogel contact lens to a temperature between to a temperature betweenminus five degree Celsius and fifteen degree Celsius, preferably betweenzero degree Celsius and twelve degree Celsius, more preferably betweentwo degree Celsius and ten degree Celsius, still more preferably betweenthree degree Celsius and eight degree Celsius so that the cooled thelens-adhere mold half with the silicone hydrogel contact lens reducesadhesion between the silicone hydrogel contact lens and the mold halfbut reduction of the adhesion is not large enough to cause the siliconehydrogel contact lens to release. According to the present application,the temperature of the mold half can be measured by any suitable method,for example, by Resistance thermometers. It is also called resistancetemperature detectors (RTDs), are sensors used to measure temperature.Many RTD elements consist of a length of fine wire wrapped around aceramic or glass core but other constructions are also used. The RTDwire is a pure material, typically platinum, nickel, or copper.

If a liquid nitrogen, liquid helium or solid carbon dioxide is used tocool the lens-adhere mold half, then too much cool (much below minusfive degree Celsius or even lower) may release the silicone hydrogelcontact lens. According to the present application, a liquid nitrogen,liquid helium or solid carbon dioxide is not used to cool thelens-adhere mold half because it is too costly. In addition, the extremelow temperature may change the dimensional in irregular way and otherproperties of the silicone hydrogel contact lens.

It is believed that, due to the reduction of adhesion force between thesilicone hydrogel contact lens and the mold half, and the presence ofareas at which the lens is separated to the mold to some degree duringdemolding process (i.e. separating male mold and female mold). During anultrasonic vibration is applied to at least one area of a non-opticalsurface of the female mold half or the male mold half having the moldedsilicone hydrogel contact lens attached thereon, these area can becomelarge and may reach the edge of the lens. In this case, air bubbles fillthe void and then the lens releases from the mold half. It is alsopossible that the delensing from the edge and moves towards the center.In this case, air is filling immediately the gap.

It is also believed that if an extra force and an ultrasonic vibrationalenergy are simultaneously applied to at least one area of the femalemold half or the male mold half having the molded silicone hydrogelcontact lens attached thereon, the separation of the molded siliconehydrogel contact lens from the mold half attached thereon will beefficient, for example, it takes less time to separate the moldedsilicone hydrogel contact lens from the mold half attached thereon willbe efficient. The extra force and the ultrasonic vibrational energy maybe applied at different areas or the same area of the female mold halfor the male mold half having the molded silicone hydrogel contact lensattached thereon. For operation simplicity, the extra force and theultrasonic vibrational energy are applied at the same area of the moldhalf. It is further believed that the extra force will deflect the moldhalf and generate additional micro air bubbles between the lens surfaceand the female mold half or the male mold half having the moldedsilicone hydrogel contact lens attached thereon.

There are several advantages associated with a method of the invention.First, combination of reduction of adhesion between the siliconehydrogel contact lens and the mold half and application of ultrasonicvibration energy enables a molded lens to be dislodged from its adheringmold half without tearing the lens. Second, lens dislodging byultrasonic vibration energy is a relatively fast process, for example,taking less than a second. Third, the present process permit siliconehydrogel lens to be separated from lens adhering mold half, and do notrequire liquid soaks. Fourth, without mold halves, an extraction tankcan accommodate much more lenses and product cost associated withextraction equipments can be decreased. Fifth, removal of the flashesand uncured polymerizable components can increase extraction efficiency.

The present invention directs to a method for producing contact lenses,comprising:

a) providing a mold including a male mold half having a first moldingsurface and a female mold half having a second molding surface, whereinthe male and female mold halves are configured to receive each othersuch that a mold cavity is formed between the first and second moldingsurfaces when the mold is closed;b) dispensing an amount of a silicone hydrogel lens-forming materialinto the female mold halves;c) mating the male and female mold halves to close the mold;d) curing thermally or actinically the silicone hydrogel lens-formingmaterial located in the mold cavity, thereby forming a silicone hydrogelcontact lens within the lens mold;e) separating the mold into the male and female mold halves, with themolded silicone hydrogel contact lens adhered on a lens-adhered moldhalf which is one of the male and female mold halves;f) cooling the lens-adhere mold half with the molded silicone hydrogelcontact lens adhered thereon to a temperature between minus five degreeCelsius and fifteen degree Celsius and provided that a liquid nitrogen,liquid helium or solid carbon dioxide is not used to cool thelens-adhere mold half;g) bringing a shaped ultrasonic horn in direct contact with at least onearea of a non-optical surface of the cooled lens-adhered mold half withthe molded silicone hydrogel contact lens attached thereon;h) applying a ultrasonic vibrational energy to the at least one area ofthe non-optical surface of the lens-adhered mold half having the moldedsilicone hydrogel contact lens attached thereon so as to release themolded silicone hydrogel contact lens from the lens-adhered mold half.

Methods of manufacturing mold sections for cast molding a contact lensare generally well known to those of ordinary skill in the art. Theprocess of the present invention is not limited to any particular methodof forming a mold. In fact, any method of forming a mold can be used inthe present invention. However, for illustrative purposes, the followingdiscussion has been provided as one embodiment of forming a mold.

In general, a mold comprises at least two mold sections (or portions) ormold halves, i.e. male and female mold halves. The male mold halfdefines a first molding (or optical) surface defining the posterior(concave) surface of a lens and the second mold half defines a secondmolding (or optical) surface defining the anterior (convex) surface of alens. The first and second mold halves are configured to receive eachother such that a lens forming cavity is formed between the firstmolding surface and the second molding surface. The molding surface of amold half is the cavity-forming surface of the mold and in directcontact with lens-forming material.

FIG. 1 schematically illustrates a preferred mold 100 used in themethods and apparatus of the invention. The mold 100 comprises a femalemold half 1 and male mold half 2.

The male mold half 2 comprises a base 61, a substantially cylindricalbody 25 which extends upward from base 61, a posterior molding surfacedefining the posterior (concave) surface of a molded contact lens, andan annular shoulder 65 which surrounds the posterior molding surface.The posterior molding surface protrudes outward from the top of body 25.The annular shoulder 65 shown is flat. It is understood that the annularshould 65 can have any suitable surface, such as, e.g., a tiltedsurface.

The female mold half 1 comprises a base 51, a substantially cylindricalbody 15 which extends upward from base 51, an anterior molding surfacedefining the anterior (convex) surface of a molded contact lens, and acollar 4. The anterior molding surface recesses downward from the top ofthe body 15. Collar 4 (or up-protruding flange) is preferably integralpart of the female mold half 1 and protrudes upward from the top of thebody 15. A circumferential groove (or recess) 11 is formed on top of thebody 15 between the anterior molding surface and functions as anoverflow for any excess unpolymerized lens-forming material.

The term “collar” as used herein refers to a peripheral circular partwhich protrude upward from the top of body of one of the two mating moldhalves. A collar can be attached to or preferably integral part of thatmold half and which can encircle the other mold half to provide a tightseal between the two mold halves. It is understood that the collar canbe provided on either of the male and female mold halves.

The female mold half 1 and a male mold half 2 are configured to receiveeach other such that a contact lens forming cavity 12 is formed betweenthe anterior and posterior molding surfaces. The collar 4 encircles thebody 25 of the male mold half 2 to provide a tight seal 5 between thefemale and male mold halves when the mold is closed. Typically, there isno lens material in the seal.

In operation, mold halves 1 and 2 can be first injection molded from aplastic resin in an injection molding apparatus, as well known to aperson skilled in the art. A specific amount of a polymerizablelens-forming material is typically dispensed into the female mold half 1by means of a dispensing device and then the male mold half 2 is put onand the mold 100 is closed (FIG. 1). As the mold 100 closes, any excessunpolymerized lens-forming material is pressed into an overflow 11provided on the female mold half 1.

Subsequently, the closed mold 100 containing the polymerizablelens-forming material is subjected to actinic irradiation (e.g., UVradiation), at least in the region of the lens forming cavity 12. Forthis purpose, at least one of the mold halves is transparent to theactinic radiation (e.g., UV light) at least in the region of the moldingsurface. Thus, at least the polymerizable lens-forming material in thelens forming cavity 12 is polymerized. It is also possible for anypolymerizable lens-forming material in the overflow 11 to bepolymerized. This is advantageous in the respect that, when the mold isopened, the excess polymerized lens-forming material then remains in theoverflow 11 of the female mold half 1, while the contact lens adheringto the male mold half 2 can be removed and further processed togetherwith male mold half 2.

The mold halves can be formed through various techniques, such asinjection molding. Methods of manufacturing mold halves for cast-moldinga contact lens are generally well known to those of ordinary skill inthe art. The process of the present invention is not limited to anyparticular method of forming a mold. In fact, any method of forming amold can be used in the present invention. The first and second moldhalves can be formed through various techniques, such as injectionmolding or lathing. Examples of suitable processes for forming the moldhalves are disclosed in U.S. Pat. No. 4,444,711 to Schad; U.S. Pat. No.4,460,534 to Boehm et al.; U.S. Pat. No. 5,843,346 to Morrill; and U.S.Pat. No. 5,894,002 to Boneberger et al., which are also incorporatedherein by reference.

Virtually all materials known in the art for making molds can be used tomake molds for making contact lenses. For example, polymeric materials,such as polyethylene, polypropylene, polystyrene, PMMA, Topas® COC grade8007-S10 (clear amorphous copolymer of ethylene and norbornene, fromTicona GmbH of Frankfurt, Germany and Summit, N.J.), or the like can beused. Other materials that allow UV light transmission could be used,such as quartz glass and sapphire.

In accordance with the invention, a silicone hydrogel lens-formingmaterial comprises at least one silicon-containing monomer or macromer,or can be any lens formulations for making soft contact lenses.Exemplary lens formulations include without limitation the formulationsof lotrafilcon A, lotrafilcon B, etafilcon A, genfilcon A, lenefilcon A,polymacon, acquafilcon A, balafilcon, senofilcon A, and the like. Alens-forming material can further include other components, such as aninitiator (e.g., a photoinitiator or a thermal initiator), a visibilitytinting agent, UV-blocking agent, photosensitizers, and the like.Preferably, a silicone hydrogel lens-forming material used in thepresent invention comprises a silicone-containing macromer orprepolymer.

Examples of silicone-containing vinylic monomers include, withoutlimitation, methacryloxyalkylsiloxanes, 3-methacryloxypropylpentamethyldisiloxane,bis(methacryloxypropyl)tetramethyl-disiloxane, monomethacrylatedpolydimethylsiloxane, mercapto-terminated polydimethylsiloxane,N-[tris(trimethylsiloxy)silylpropyl]acrylamide,N-[tris(trimethylsiloxy)silylpropyl]methacrylamide,tris(pentamethyldisiloxyanyl)-3-methacrylatopropylsilane (T2), andtristrimethylsilyloxysilylpropyl methacrylate (TRIS). A preferredsiloxane-containing monomer is TRIS, which is referred to3-methacryloxypropyltris(trimethylsiloxy) silane, and represented by CASNo. 17096-07-0. The term “TRIS” also includes dimers of3-methacryloxypropyltris(trimethylsiloxy) silane.

Any suitable siloxane-containing macromer with ethylenically unsaturatedgroup(s) can be used to produce a silicone hydrogel material. Aparticularly preferred siloxane-containing macromer is selected from thegroup consisting of Macromer A, Macromer B, Macromer C, and Macromer Ddescribed in U.S. Pat. No. 5,760,100, herein incorporated by referencein its entirety. Macromers that contain two or more polymerizable groups(vinylic groups) can also serve as cross linkers. Di and triblockmacromers consisting of polydimethylsiloxane and polyakyleneoxides couldalso be of utility. Such macromers could be mono or difunctionalizedwith acrylate, methacrylate or vinyl groups. For example one might usemethacrylate end cappedpolyethyleneoxide-block-polydimethylsiloxane-block-polyethyleneoxide toenhance oxygen permeability.

Examples of silicone-containing prepolymers include without limitationthose disclosed in US Patent Application Publication No. US 2001-0037001A1 and U.S. Pat. No. 6,039,913, which are incorporated herein byreferences in their entireties. Preferably, the prepolymers used in theinvention are previously purified in a manner known per se, for exampleby precipitation with organic solvents, such as acetone, filtration andwashing, extraction in a suitable solvent, dialysis or ultrafiltration,ultrafiltration being especially preferred. By means of thatpurification process the prepolymers can be obtained in extremely pureform, for example in the form of concentrated aqueous solutions that arefree, or at least substantially free, from reaction products, such assalts, and from starting materials, such as, for example, non-polymericconstituents. The preferred purification process for the prepolymersused in the process according to the invention, ultrafiltration, can becarried out in a manner known per se. It is possible for theultrafiltration to be carried out repeatedly, for example from two toten times. Alternatively, the ultrafiltration can be carried outcontinuously until the selected degree of purity is attained. Theselected degree of purity can in principle be as high as desired. Asuitable measure for the degree of purity is, for example, theconcentration of dissolved salts obtained as by-products, which can bedetermined simply in known manner.

In accordance with the present invention, a silicone hydrogellens-forming material can also comprise a hydrophilic vinylic monomer.Nearly any hydrophilic vinylic monomer that can act as a plasticizer canbe used in the fluid composition of the invention. Among the preferredhydrophilic monomers are N,N-dimethylacrylamide (DMA),2-hydroxyethylmethacrylate (HEMA), hydroxyethyl acrylate, hydroxypropylacrylate, hydroxypropyl methacrylate (HPMA), trimethylammonium 2-hydroxypropylmethacrylate hydrochloride, dimethylaminoethyl methacrylate(DMAEMA), dimethylaminoethylmethacrylamide, acrylamide, methacrylamide,allyl alcohol, vinylpyridine, glycerol methacrylate,N-(1,1dimethyl-3-oxobutyl)acrylamide, N-vinyl-2-pyrrolidone (NVP),acrylic acid, methacrylic acid, and N,N-dimethyacrylamide (DMA).

A silicone hydrogel lens-forming material can also comprises ahydrophobic monomer. By incorporating a certain amount of hydrophobicvinylic monomer in a polymerizable fluid composition, the mechanicalproperties (e.g., modulus of elasticity) of the resultant polymer may beimproved.

A silicone hydrogel lens-forming material can further comprise anantimicrobial agent, preferably antimicrobial metal nanoparticles, morepreferably silver nanoparticles.

A specific amount of a polymerizable lens-forming material is typicallydispensed into a female mold half by means of a dispensing device andthen a male mold half is put on and the mold is closed. As the moldcloses, any excess unpolymerized lens-forming material is pressed intoan overflow provided on the female mold half (or alternatively on themale mold half).

The closed mold containing the polymerizable lens-forming materialsubsequently is cured. A person skilled in the art knows well how tocure a lens-forming material. For example, a lens-forming material issubjected to actinic irradiation (e.g., UV radiation) at least in theregion of the lens forming cavity or thermal treatment (e.g., heating inan oven) to form a lens. For actinic curing, at least one of the moldhalves is transparent to the actinic radiation (e.g., UV light) at leastin the region of the molding surface. Thus, at least the polymerizablelens-forming material in the lens forming cavity is polymerized. It isalso possible for any polymerizable lens-forming material in theoverflow to be polymerized. This is advantageous in the respect that,when the mold is opened, the excess polymerized lens-forming materialthen remains in the overflow of the female mold half, while the contactlens adhering to the male mold half can be removed and further processedtogether with male mold half.

Subsequently, applying a force to non-optical surface of the female moldat a location about the center area of non-optical molding surface at anangle of less than about 30 degrees, preferably less than about 10degrees, most preferably less than about 5 degrees (i.e., in a directionsubstantially normal to center area of non-optical molding surface)relative to the axis of the mold to deform the female mold surface whichbreaks the bonds between the optical molding surface of the female moldand the lens, as shown in FIG. 2. Various ways of applying a force tonon-optical surface of the female mold at a location about the centerarea of non-optical molding surface along the axis of the mold to deformthe female mold surface which breaks the bonds between the opticalmolding surface of the female mold and the lens. It is understood thatthe mold-opening device can have any configurations known to a personskilled in the art for performing the function of separating two moldhalves from each other. For example, referring to FIG. 2, the demoldingassembly comprises a pin 70 positionable against the center area ofnon-optical molding surface of the female mold section. The pin 70 has aflat free end 70 a to enable a surface contact between the free end 70 aand the center area of non-optical molding surface of the female mold.It will be appreciated that the scope of the invention is not limited tosuch a particular flat configuration of the pin end 70 a, for examplethe pin may have a rounded free end. In the present embodiment, the pin70 is movable and the female mold remains stationary by applying arestraining force to female mold half applying a restraining force tofemale mold half with a first prying finger 32 for maintaining thefemale mold half in a fixed position. However, it is possible to arrangethe assembly so that the female mold is movable and the pin 70 remainsstationary, or so that both the pin 70 and the female mold can be movedrelative to each other.

In use, during the demolding operation, the free end 70 a of the pin 70applies a longitudinally directed force to the central portion of thenon-optical surface of the female mold. The first prying finger 32applies a counteractive force against the end face 51 a of the flange 51of the female mold section 1. Consequently, the female mold section iscompressed between the free end 70 a of the pin 70 and the first finger32. The compression force deforms the curved part of the female moldsection and breaks the adhesive bond between the lens-forming opticalsurface of the female mold section 1 and the anterior surface of thelens 12.

Then, apply a vertical lifting movement to the male mold with a secondprying finger (while maintaining the restraints on the female mold so asto effectuate gradual separation between the female mold and the malemold.

After separating the male mold and the female mold, the contact lensadheres to the male mold even though the molding surfaces of the femalemold and male mold are not treated before or after dispensing a specificamount of a polymerizable lens-forming material into one of the moldhalves to render the molded contact lens preferentially adhered to thefemale mold or male mold when separating the mold.

After breaking the bond between the optical molding surface of thefemale mold and the lens, the mold is separated, the molded contact lensadhering to the male mold half 2. It is surprising to find out that,according to the present invention, the molded contact lens adhering tothe male mold half even though the molding surfaces of the female moldand male mold are not treated before or after dispensing a specificamount of a polymerizable lens-forming material into one of the moldhalves to render the molded contact lens preferentially adhered to thefemale mold or male mold when separating the mold.

Once the mold sections have been separated, the lens will adhere to asurface of the male mold sections and must therefore be released fromthe male mold section. According to the present application as mentionedabove, the lens typically remains adhered to the male mold section.However, by using similar principle, the compression can be applied tothe applying a force to non-optical surface of the male mold at alocation about the center area of non-optical molding surface along thelongitudinal axis of the mold to deform the male mold to compress thefemale mold between the pin and the first set of pry fingers so as tobreak the bonds between the optical molding surface of the male mold andthe lens, thereby the lens adhere to the female mold when separating themold.

According to the present application, an ultrasonic welding system isused not to welding two pieces of plastic material together but toseparate molded silicone hydrogel contact lens from the mold halfattached thereon. An ultrasonic welding system as illustrated in FIG. 3comprises: a power supply (300) which provides a high power AC signalwith frequency matching the resonance frequency of the ultrasonic stack.An ultrasonic stack composed of a converter (310), a booster 320) and ahorn (330). All three elements of the stack are specifically tuned toresonate at the same exact ultrasonic frequency (Typically 15, 20, 30,35, 40 or 70 kHz). The converts the electrical signal into a mechanicalvibration. The booster modifies the amplitude of the vibration. The horncan also define the amplitude of vibration and apply the mechanicalvibration to the parts to be contacted. However, any kind of mechanicalsystem which transfers the vibrational energy from the conver to themold half can be used.

FIG. 4 illustrates an embodiment of the invention is shown wherein anultrasonic horn (330) having a flat surface (340) is sized to beapproximately the outer diameter of the male mold half (2) and seated onextended flat edge surround the outer concave surface (35) (or backsurface of the annular shoulder 65) of the male mold half. The male moldhalf (2) proximate the ultrasonic horn vibrates with the acousticalenergy emitted from the ultrasonic horn (330) while the contact lens(85) is attached thereon so that a relative motion at the frequency ofthe acoustic energy takes place between back surface of the annularshoulder (65) of the male mold half and the contact lens attachedthereon. The male mold half and the contact lens attached thereon isheld stationary by a position holder (75). A person skilled in the artknows which device can be used as a position holder, for example, alevel metal or a cup having an attached level metal. The cup can be usedto collect the lens separated from the male mold half. Furthermore, thecup can be attached a vacuum source and the vacuum can assist theseparation of the lens from the male mold half.

FIGS. 5A and 5B show an embodiment wherein an ultrasonic horn (330)having a convex surface (340) is of a size that allows it to extendwithin the outer concave portion of male half mold half (2). The malemold half and the contact lens (85) attached thereon is held stationaryby a position holder (75). FIG. 5A illustrates that the ultrasonic hornvibrates with the acoustical energy emitted from the ultrasonic horn(330) while the contact lens is attached thereon so that a relativemotion at the frequency of the acoustic energy takes place throughcontact surface between inside of the outer concave portion of male halfmold half (2) and the contact lens attached thereon. 5B illustrates thatthe ultrasonic horn vibrates with the acoustical energy emitted from theultrasonic horn (330) while the contact lens is attached thereon so thata relative motion at the frequency of the acoustic energy takes placethrough contact points between edges of the outer concave portion ofmale half mold half 2 and the contact lens attached thereon.

FIG. 6 illustrates an embodiment of the invention is shown wherein anultrasonic horn (330) having a flat surface (340) is sized to beapproximately the outer diameter of the female mold half (1) to contactthe center area of the outer convex portion of the female mold half. Thefemale mold half and the contact lens (85) attached thereon is heldstationary by a position holder (75). The center portion of back surface(non-optical surface) of the female mold half (1) proximate theultrasonic horn vibrates with the acoustical energy emitted from theultrasonic horn (330) while the contact lens is attached thereon so thata relative motion at the frequency of the acoustic energy takes placebetween the female mold half and the contact lens attached thereon.

FIGS. 7A and 7B show an embodiment wherein an ultrasonic horn (330)having a concave surface (340) is of a size that allows it to extendwithin the outer convex portion of female half mold half (1) to contactthe center area of the outer convex portion of the female mold half. Thefemale mold half and the contact lens (85) attached thereon is heldstationary by a position holder (75). FIG. 7A illustrates that theultrasonic horn vibrates with the acoustical energy emitted from theultrasonic horn (330) while the contact lens is attached thereon so thata relative motion at the frequency of the acoustic energy takes placethrough contact surface between inside of the outer convex portion offemale half mold half 1 and the contact lens attached thereon. 7Billustrates that the ultrasonic horn vibrates with the acoustical energyemitted from the ultrasonic horn (330) while the contact lens isattached thereon so that a relative motion at the frequency of theacoustic energy takes place through contact points between edges of theouter concave portion of female half mold half 1 and the contact lensattached thereon.

FIG. 8 illustrates an embodiment of the invention is shown wherein thelens-adhere mold half with the silicone hydrogel contact lens adheredthereon is cooled with a cold air blower (140), such as a VORTEC ColdAir Gun or the AirJet unit, both convert compressed air to a lowertemperature, by blowing cold air onto the inside of the outer concaveportion (non-optical side) of male half mold half (2) or by blowing coldair onto the surface of the silicone hydrogel contact lens, providedthat a liquid nitrogen, liquid helium or solid carbon dioxide is notused to cool the lens-adhere mold half.

FIG. 9 illustrates an embodiment of the invention is shown wherein thelens-adhere mold half with the silicone hydrogel contact lens adheredthereon is cooled through direct contact between the surface 341 of acold device, such as a cold hollow tube 141 with a closed surface 341 atone end of the tube and the surface 251 of the inside of the outerconcave portion (non-optical side) of male half mold half (2), providedthat a liquid nitrogen, liquid helium or solid carbon dioxide is notused to cool the lens-adhere mold half. The temperature of the hollowtube with the closed surface 341 is reduced with a cold air blower(140), such as a VORTEC Cold Air Gun or the AirJet unit, both convertcompressed air to a lower temperature, to provide temperature from minus20 degree Celsius to minus 80, degree Celsius to blow cold air onto theinside of the tube through inlet 142 for about one to three seconds andcold air flowing out through outlet 143.

FIG. 10 illustrates an embodiment of the invention is shown wherein thelens-adhere mold half with the silicone hydrogel contact lens adheredthereon is cooled by flowing a cold air directed through a cold hollowtube 141 without a closed surface at one end of the tube directly to theinside of the outer concave portion (non-optical side) of male half moldhalf (2), provided that a liquid nitrogen, liquid helium or solid carbondioxide is not used to cool the lens-adhere mold half. The cold air isgenerated by cold air blower (140), such as a VORTEC Cold Air Gun or theAirJet unit, both convert compressed air to a lower temperature, toprovide temperature from minus 20 degree Celsius to minus 80, degreeCelsius to blow cold air onto the inside of the tube through inlet 142for about one to three seconds and cold air flowing out through outlet143.

Furthermore, a Peltier device can be used to cool down the hollow tube.Thermoelectric coolers operate by the Peltier effect (which also goes bythe more general name thermoelectric effect). The device has two sides,and when a DC electric current flows through the device, it brings heatfrom one side to the other, so that one side gets cooler while the othergets hotter. The “hot” side is attached to a heat sink so that itremains at ambient temperature, while the cool side goes below roomtemperature. In special applications, multiple coolers can be cascadedtogether for lower temperature, but overall efficiency dropssignificantly. The Peltier effect is the presence of heating or coolingat an electrified junction of two different conductors.

According to the present invention, the modification to the output partof the horn and the preferred parameters associated with operating thesystem are given in the following. The ultrasonic welding system iscomprised of a power supply (300) which generates a frequency range from15 kHz to 70 kHz by the use of solid state power devices. This highfrequency electrical energy is supplied to a converter (320). Thiscomponent changes the electrical energy into ultrasonic mechanicalvibratory energy at the frequency of the converted electrical energysupply which is typically 15 kHz to 70 kHz. The vibratory ultrasonicacoustical energy is then transmitted through an amplitude modifyingdevice called a booster (320). The booster is a passive (i.e.,non-powered) device which is used to modify the output amplitude of theconverter before it reaches the horn (330). The horn is shaped to hornhaving a flat surface, convex surface or a concave surface, etc (340) isan acoustical tool that transfers the vibratory energy directly to thenon-optical surface of a mold half. The present invention is practicedwith the above described apparatus as follows: an ultrasonic weldingapparatus as described above, the specific system being used for theinvestigation is a Dukane iQ Series ES Servo Ultrasonic Welding PressSystem with a 30 kHz generator, 2:1 booster. The generator creates auser settable, high voltage (1000 Vrms), 30 kHz signal that is appliedto the transducer. The transducer expands and contract with this appliedvoltage and creates a mechanical vibration at the face of thetransducer. This vibration is amplified by the booster and hornassembly. The end effect of the ultrasonic process is to produce avertical displacement of the horn. The amount of vertical displacementis a factor of the following: frequency, booster gain, horn gain (horndesign) and amplitude. According to the present patent application, thevertical displacement ranges from 20 to 160 micron, preferably between80 to 140 micron, still more preferably between 100 to 120 micron. Tomaximize the effectiveness of the mechanical vibration on the part, thevibration needs to be applied in a prescribed manner.

To operate the Dukane Servo system, the ultrasonic horn is lowered to apoint in space, where it begins to look for a reaction force equal tothe trigger force set by the user. It will continue to move downward atprescribed speed over a short distance looking for that reaction force.When that force is achieved, the system will fire the ultrasonics. Oncefired, the horn will seek to move to maintain that constant force. Forcemode was chosen to deal with the normal positional variation you wouldencounter with different parts placed slightly differently from theprevious part, as well as slight geometry variations from part to part.The generator output energy equals to the time integral of power.

In another aspect, the invention is directed to an apparatus fordelensing a hydrogel contact lens from the lens adhering mold half,separating a molded hydrogel contact lens from a female mold half or amale mold half attached thereon, the apparatus comprising:

means for holding the female mold half or the male mold half havinghydrogel contact lens attached thereon stationary,

means for cooling the lens-adhere mold half with the silicone hydrogelcontact lens adhered thereon; an ultrasonic energy horn is shaped todirect contact with at least one area of a non-optical surface of thefemale mold half or the male mold half having the molded hydrogelcontact lens attached thereon,

a power supply, a converter and a booster coupled to the horn to form aultrasonic welding system for generating ultrasonic energy of afrequency and amplitude, and for a duration necessary to separate themolded hydrogel contact lens from the female mold half or the male moldhalf attached thereon.

Example 1

Chemicals

The following abbreviations are used in the following examples: VAZO 64represents 2,2′-dimethyl-2,2′azodipropiononitrile; Nobloc is2-[3-(2H-Benzotriazol-2-yl)-4-hydroxyphenyl] ethyl methacrylate fromAldrich; UV28 represents2-{2′-Hydroxy-3′-tert-butyl-5′-[3′-methacryloyloxypropoxy]phenyl}-5-chloro-2H-benzotriazole;RB247 is Reactive Blue 247; PrOH represents 1-propanol; PBS represents aphosphate-buffered saline which has a pH of 7.2±0.2 at 25° C. andcontains about 0.044 wt. % NaH2PO4.H2O, about 0.388 wt. % Na2HPO4.2H2O,and about 0.79 wt. % NaCl and; wt. % represents weight percent;

Preparation of CE-PDMS Macromer

In the first step,.alpha.,.omega.-bis(2-hydroxyethoxypropyl)-polydimethylsiloxane(Mn=2000, Shin-Etsu, KF-6001a) is capped with isophorone diisocyanate(IPDI) by reacting 49.85 g of.alpha.,.omega.-bis(2-hydroxyethoxypropyl)-polydimethylsiloxane with11.1 g IPDI in 150 g of dry methyl ethyl ketone (MEK) in the presence of0.063 g of dibutyltindilaurate (DBTDL). The reaction is kept for 4.5 hat 40.degree. C., forming IPDI-PDMS-IPDI. In the second step, a mixtureof 164.8 g of.alpha.,.omega.-bis(2-hydroxyethoxypropyl)-polydimethylsiloxane(Mn=3000, Shin-Etsu, KF-6002) and 50 g of dry MEK are added dropwise tothe IPDI-PDMS-IPDI solution to which has been added an additional 0.063g of DBTDL. The reactor is held for 4.5 h at about 40.degree. C.,forming HO-PDMS-IPDI-PDMS-IPDI-PDMS-OH. MEK is then removed underreduced pressure. In the third step, the terminal hydroxyl-groups arecapped with methacryloyloxyethyl groups in a third step by addition of7.77 g of isocyanatoethylmethacrylate (IEM) and an additional 0.063 g ofDBTDL, forming IEM-PDMS-IPDI-PDMS-IPDI-PDMS-IEM (i.e., CE-PDMSterminated with methacrylate groups).

Alternate Preparation of CE-PDMS Macromer with Terminal MethacrylateGroups 240.43 g of KF-6001 is added into a 1-L reactor equipped withstirring, thermometer, cryostat, dropping funnel, and nitrogen/vacuuminlet adapter, and then dried by application of high vacuum(2.times.10.sup.-2 mBar). Then, under an atmosphere of dry nitrogen, 320g of distilled MEK is then added into the reactor and the mixture isstirred thoroughly. 0.235 g of DBTDL is added to the reactor. After thereactor is warmed to 45.degree. C., 45.86 g of IPDI are added through anaddition funnel over 10 minutes to the reactor under moderate stirring.The reaction is kept for 2 hours at 60.degree. C. 630 g of KF-6002dissolved in 452 g of distilled MEK are then added and stirred until ahomogeneous solution is formed. About 0.235 g of DBTDL is added, and thereactor is held at about 55.degree. C. overnight under a blanket of drynitrogen. The next day, MEK is removed by flash distillation. Thereactor is cooled and 22.7 g of IEM are then charged to the reactorfollowed by about 0.235 g of DBTDL. After about 3 hours, an additional3.3 g of IEM are added and the reaction is allowed to proceed overnight.The following day, the reaction mixture is cooled to about 18.degree. C.to obtain CE-PDMS macromer with terminal methacrylate groups.

Preparation of Polymerizable Compositions

A lens formulation is prepared by dissolving components to have thefollowing composition: 40% by weight of CE-PDMS macromer prepared inExample 2, 28% by weight ofN-[tris(trimethylsiloxy)-silylpropyl]acrylamide (TRIS-Am), 32% by weightof N,N-dimethylacrylamide (DMA), 1.5% by weight of Norbloc, 0.5% byweight VAZO, 0.4% by weight of UV28, 0.01% by weight of RB247, and 5% byweight of 1-propanol.

Cast Molding

The formulation prepared above is introduced into a polypropylene molds.Then, the molds are dosed and thermally cured in an oven under nitrogenusing the following temperature conditions: at 55° C. for 40 minutes; at80° C. for 40 minutes; and at 100° C. for 40 minutes.

Mold Separation

Lens molds each with a molded silicone hydrogel contact lens precursortherein are mechanically opened as illustrated by FIG. 2 and describedabove. The molded unprocessed silicone hydrogel contact lens precursorsadhere to the male mold halves.

Removing Lens Precursors from Lens-Adhered Mold Halves

Molded silicone hydrogel contact lens are removed (i.e., “delensed”)from lens-adhered male mold halves by first cooling the lens-adhere moldhalf with the silicone hydrogel contact lens adhered thereon to atemperature of about from minus five to fifteen degree Celsius byapplying a cold air of about minus twenty degree Celsius to the moldhalf for 2 to 10 second (FIG. 10), then using an ultrasonic weldingapparatus as illustrated in FIG. 3. An ultrasonic horn made of stainlesssteel and having a shape shown in FIG. 4.

Lens molds each with a molded silicone hydrogel contact lens therein aremechanically opened as illustrated by FIG. 2 and described above. Themolded silicone hydrogel contact lens adhere to the male mold halves.

The lens-adhere mold half with the silicone hydrogel contact lensadhered thereon is cooled with a cold air blower as illustrated by FIG.8.

bringing a shaped ultrasonic horn in direct contact with at least onearea of a non-optical surface of the cooled lens-adhered mold half withthe molded silicone hydrogel contact lens attached thereon.

applying a ultrasonic vibrational energy to the at least one area of thenon-optical surface of the lens-adhered mold half having the moldedsilicone hydrogel contact lens attached thereon so as to remove themolded silicone hydrogel contact lens from the lens-adhered mold half.

Example process settings are provided as follow:

Process Parameter Setting Generator Frequency 30 or 40 kHz Booster 2:1Horn 2:1 Trigger Force 100N Energy 0.1-40 J

According to the present invention, Generator Frequency is operatedbetween 15 kHz to 70 kHz, preferably between 20 kHz to 40 kHz, morepreferably between 30 kHz to 40 kHz, inclusive. Trigger Force isoperated between 1.0 N to 200N, preferably between 20 N to 150N, morepreferably between 50 N to 110N, still more preferably between 75 N to100N. Energy is operated between 0.1 J to 40 J, preferably between 0.5 Jto 30 J, still more preferably between 1.0 J to 20 J. The duration ofapplying the ultrasonic vibration energy necessary to separate themolded hydrogel contact lens from the female mold half or the male moldhalf attached thereon is typically less than 10 seconds, preferably lessthan 5.0 seconds, more preferably less than 2.0 seconds, still morepreferably less than 1.0 second.

Results:

Trial Sample size, N= Yield, % 1 20 90 2 15 87 3 20 70 4 20 75 5 15 87

For the above trials, the average yield is 82 percent and processparameters are as follows: cooling the lens-adhere mold half with thesilicone hydrogel contact lens adhered thereon to a temperature of about3.5 degree Celsius by applying a cold air blower (VORTEC Cold Air Gun,or the AirJet unit, both convert compressed air to a lower temperature),delens the lens from the BC mold using the 30 kHz ultrasonic delenserwith the curved horn and 2.0 booster using a force applied to the BCmold of 75-150 N, a delensing energy of 1-8 J, a delensing amplitude of80-100%, and a delensing ramp up time of 20-50 ms. Comparing to thecontrol which has the same operation conditions except of on coolingsteps, the trial results is at least 50 percent higher. Please also noteafter cooling treatment, 100% of the molded silicone hydrogel contactlens are still adhered to the mold half.

It is understood that methods of manufacturing mold halves for castmolding a contact lens are generally well known to those of ordinaryskill in the art. The process of the present invention is not limited toany particular method of forming a mold half. In fact, any method offorming a mold half can be used in the present invention. However, forillustrative purposes, the above discussion has been provided as oneembodiment of forming mold halves that can be used in accordance withthe present invention.

Various embodiments are evident. Although one mold (FIG. 1) isillustrated, the invention is in no way limited to this specific mold. Aperson skilled in the art can readily determine other molds for whichthe invention has applicability.

The invention has been described in detail, with particular reference tocertain preferred embodiments, in order to enable the reader to practicethe invention without undue experimentation. A person having ordinaryskill in the art will readily recognize that many of the previouscomponents, compositions, and/or parameters may be varied or modified toa reasonable extent without departing from the scope and spirit of theinvention. Furthermore, titles, headings, example materials or the likeare provided to enhance the reader's comprehension of this document, andshould not be read as limiting the scope of the present invention.Accordingly, the invention is defined by the following claims, andreasonable extensions and equivalents thereof.

What is claimed is:
 1. A method for producing contact lenses,comprising: a) providing a mold including a male mold half having afirst molding surface and a female mold half having a second moldingsurface, wherein the male and female mold halves are configured toreceive each other such that a mold cavity is formed between the firstand second molding surfaces when the mold is closed; b) dispensing anamount of a silicone hydrogel lens-forming material into the female moldhalves; c) mating the male and female mold halves to close the mold; d)curing thermally or actinically the silicone hydrogel lens-formingmaterial located in the mold cavity, thereby forming a silicone hydrogelcontact lens within the lens mold; e) separating the mold into the maleand female mold halves, with the molded silicone hydrogel contact lensadhered on a lens-adhered mold half which is one of the male and femalemold halves; f) cooling the lens-adhere mold half with the moldedsilicone hydrogel contact lens adhered thereon to a temperature betweenminus five degree Celsius and fifteen degree Celsius and provided that aliquid nitrogen, liquid helium or solid carbon dioxide is not used tocool the lens-adhere mold half; g) bringing a shaped ultrasonic horn indirect contact with at least one area of a non-optical surface of thecooled lens-adhered mold half with the molded silicone hydrogel contactlens attached thereon; h) applying a ultrasonic vibrational energy tothe at least one area of the non-optical surface of the lens-adheredmold half having the molded silicone hydrogel contact lens attachedthereon so as to release the molded silicone hydrogel contact lens fromthe lens-adhered mold half.
 2. The method of claim 1, wherein the shapedultrasonic horn is a flat ultrasonic horn.
 3. The method of claim 1,wherein the shaped ultrasonic horn is a convex ultrasonic horn.
 4. Themethod of claim 1, wherein the shaped ultrasonic horn is a concaveultrasonic horn.
 5. The method of claim 1, wherein applying anultrasonic vibrational energy is operated with a Generator Frequencybetween 15 kHz to 50 kHz.
 6. The method of claim 1, wherein applying anultrasonic vibrational energy is triggered by a force between 1.0 N to150N.
 7. The method of claim 1, wherein applying an ultrasonicvibrational energy produces a vertical displacement of the ultrasonichorn ranging from 20 to 160 micron.
 8. The method of claim 1, whereincuring step is thermally curing.
 9. The method of claim 1, wherein thecooling the lens-adhere mold half with a cold air blower to blow a coldair onto the non-optical side of the lens-adhere mold half.
 10. Themethod of claim 1, wherein the cooling the lens-adhere mold half with acold horn to directly contacting the non-optical side of the lens-adheremold half.
 11. The method of claim 10, wherein the cooling device is ashaped horn.
 12. The method of claim 1, wherein cooling the lens-adheremold half to a temperature between minus zero degree Celsius and twelvedegree Celsius.
 13. The method of claim 12, wherein the cooling thelens-adhere mold half to a temperature between two degree Celsius andten degree Celsius.
 14. The method of claim 13, wherein the cooling thelens-adhere mold half to a temperature between three degree and eightdegree.
 15. An apparatus for delensing a hydrogel contact lens from thelens adhering mold half, separating a molded hydrogel contact lens froma female mold half or a male mold half attached thereon, the apparatuscomprising: means for holding the female mold half or the male mold halfhaving hydrogel contact lens attached thereon stationary, means forcooling the lens-adhere mold half with the silicone hydrogel contactlens adhered thereon; an ultrasonic energy horn is shaped to directcontact with at least one area of a non-optical surface of the femalemold half or the male mold half having the molded hydrogel contact lensattached thereon, a power supply, a converter and a booster coupled tothe horn to form a ultrasonic welding system for generating ultrasonicenergy of a frequency and amplitude, and for a duration necessary toseparate the molded hydrogel contact lens from the female mold half orthe male mold half attached thereon.